The present technology for wirewound resistors consists of a cylindrical ceramic core to which metal end caps are attached on each end. Wire terminals are then attached to the metal end caps. Resistance wire is wound around the ceramic core and affixed in some manner to the metal end caps. This unit is then encapsulated using various techniques and encapsulating materials to provide protection to the resistance wire from various environments to which they may be exposed. This is a proven design as evidenced by the excellent reliability these resistors have demonstrated for millions of users in a wide variety of applications. They are known for their high reliability; excellent resistance stability, with low temperature coefficient; and their ability to dissipate large amounts of power utilizing a small package size when compared to other resistor technologies.
A major drawback to this design in today's state of high automation is that this design requires considerable expense by the end customer to install the resistor into a circuit board. The circuit board must have holes placed in it which are suitable in size to accept the resistor terminals. The resistor terminals must then be cut to the proper length and formed in some manner so the terminals may be inserted into the holes in the circuit board. The terminals are then permanently attached to the circuit board using any number of circuit board soldering techniques such as infrared reflow or wave soldering. Circuit board designers utilizing this technology are limited to mounting components on only one side of the circuit board as the resistor terminals protrude through the circuit board.
It is, therefore, a principal object of this invention to provide a surface mount resistor which can be mounted to terminals on a circuit board without creating holes in the circuit board or without cutting the resistor terminals.
It is a further object of this invention to provide a surface mount resistor which can be mounted on either or both sides of the circuit board.
A still further object of the invention is to provide a surface mount resistor which will require less space on the circuit board since the terminals are an integral part of the surface mount component.
A still further object of the invention is to provide a surface mount resistor which is compatible with automated circuit board manufacturing equipment and techniques, and which can be economically manufactured.
A still further object of this invention is to provide a method of manufacturing a surface mount wirewound resistor which is economical and efficient from a manufacturing standpoint.
These and other objects will be apparent to those skilled in the art.